The present invention relates in general to weighing apparatus, and more particularly to a weighing apparatus suitable for use with a vehicle having tines.
Pallet jacks or pallet trucks have heretofore been employed for weighing a pallet with a load thereon during the carrying of the pallet. Such apparatus have employed strain gauge load cells, which produce electrical signals representative of the weight of the pallet and the load thereon. The signals are applied to a digital display to give a read-out of the weight of the pallet and the load carried by the pallet. One of such apparatus has been advertised in a brochure entitled Mobile Universal - Waage HY-UW 2000.
Strain gauge load cells are prone to being damaged when subjected to intense forces and/or shock exceeding their rated capacity. The replacement of load cells has been generally costly. When a pallet jack, or other such vehicle that comprises tines for carrying a load, is equipped with a weighing apparatus that includes one or several strain gauge load cells, intense forces and/or shocks can easily occur at the time that the tines are inserted under the load to be moved.
In the case of a pallet jack, when a pallet with a load thereon is to be moved, the tines are generally inserted in the center of the pallet, below the deck boards. In doing so, the center post of the pallet may be hit by one of the tines. This shock can be mechanically transmitted to the load cells. Further, when the front wheels of the tines roll over the bottom outer board of the pallet, the resulting shock can also be mechanically transmitted to the load cells.
In addition, when the tines are not placed at their lowest possible position, they can become wedged between the top and bottom outer boards of the pallet. The operator of the pallet jack may then try to force the tines under the pallet. This action can result in intense forces being mechanically transmitted to the load cells.
When the pallet reaches the end of its movement over the tines and comes to rest against a mechanical stop, which is necessary to prevent the pallet from coming into contact with the non-weighing part of the pallet jack, an additional shock and/or intense force can be mechanically transmitted to the load cells.
The U.S. Pat. to Raz, No. 4,666,004, issued on May 19, 1987, for Pallet Truck With Weighing Scale, discloses a pallet truck with load cells mounted on the tines for weighing loads carried by the pallet truck. Floating members are disposed over the tines and extend along the entire length of the tines to provide the weighing surfaces. A crosspiece provides rigidity for the floating members.
The U.S. Pat. to Cellitti et al., No. 2,935,213, issued on May 3, 1960, for Fork Lift Vehicle Weighing Scale, discloses a forklift vehicle having weighing scale forklift tines. Each of the tines includes a longitudinal bar that is mounted on the associated tine and is slightly elevated with respect to the end portions of the associated tine. Load cells respond to the vertical weighing movement of the longitudinal bars. Each of the tines is provided with a front bearing plate that is secured to the associated tine forward of the associated longitudinal bar.
In the U.S. Pat. to Pien, No. 3,059,710, issued on Oct. 23, 1962, for Indirect Measurement of Vertical Forces, there is disclosed a load supporting member for a forklift truck with weighing apparatus. The load supporting member is a cantilevered member which applies forces to the strain gauge load cell commensurate with the weight of the load. One end of the load supporting member is the free end that moves vertically in response to the weight of the load. The other end of the load supporting member is fixed to the nose of the tine. There is a rigid connection between the proximal end of the load supporting member and the nose of the tine. A pallet moving onto the tine first engages the nose of the tine and then advances onto the load supporting member.
In the U.S. Pat. No. to Russo, No. 4,420,053, issued on Dec. 13, 1983, for Fork Lift Weighing Apparatus, there is disclosed a fork for lifting a load. A weighing bridge and load cells are disposed within a recess of the fork. Disc shock absorbers of hard rubber are disposed between the weighing bridge and the load cells.
The U.S. Pat. No. to Wise, No. 2,643,781, issued on June 30, 1953, for Load Weighing System For Lift Trucks And The Like, discloses a forklift with an hydraulic scale installed on the forklift to enable a load to be weighed at the same time it is lifted by the fork. The U.S. Pat. No. to Hofmeister, No. 3,063,576, issued on Nov. 13, 1962, for Weighing Means For Fork-Lift Trucks, discloses a forklift truck with forks for lifting a load. Each fork has a bar extending thereover that is supported at each end by a load cell.
In the U.S. Pat. No. to Airesman, No. 3,910,363, issued on Oct. 7, 1975, for Weighing Device For Fork Lift Truck, there is disclosed a forklift truck with forks to lift a load. A movable plate for the forklift truck is moved vertically downward when the load is lifted by the fork. Load cells are coupled to the movable plate for providing electrical signals proportionate to the load in response to the vertical movement of the movable plate. Overload stops are provided to limit the downward vertical movement of the movable plate to reduce damage to the load cells.
In the U.S. Pat. No. to Curran, No. 4,589,507, issued on May 20, 1986, for On Board Scale Devices, there is disclosed an on board scale used in conjunction with a truck, trailer or the like to obtain the weight of various freight items placed thereon. The scale includes retractable pneumatic scale assemblies for weighing the freight. The U.S. Pat. No. to Baldwin et al., No. 4,638,876, issued on Jan. 27, 1987, for Weighing Apparatus, discloses a weighing apparatus for use with a forklift. The weighing apparatus includes a weighing plate on which the load is placed. Three load cells engage the weighing plate. Lines connecting the load cells define a triangle.